Real-time spectrum analyzers (RTSAs) such as the RSA6100, RSA5100, and RSA3400 families available from Tektronix, Inc. of Beaverton, Oregon trigger on, capture, and analyze RF signals in real-time. These test and measurement instruments seamlessly capture RF signals so that, unlike conventional swept spectrum analyzers and vector signal analyzers, no data is missed within a specified bandwidth.
FIG. 1 is a simplified block diagram of portions of an RTSA. A mixer 105 in conjunction with a local oscillator 106 converts or tunes the input, which may also be filtered, to an intermediate frequency (IF). A filter 115 may further refine the IF signal before it is passed to an analog-to-digital (A/D) converter 120 to provide a digital signal for further processing. The digital signal is passed to a processor 130 that provides triggering, memory, and analysis functions. In some embodiments the memory 132 may be implemented using a circular buffer. When the trigger generator 136 detects a trigger event, a trigger signal is generated that causes the memory 132 to store a seamless block of digital data from the digital signal for subsequent processing by a digital signal processor 134, or for offloading to another processor (not shown) for non-real-time post-processing. A user may select a particular view 140 for viewing the measured signal on a display device 150.
Historically, spectrum analyzers use detectors to determine what signal power value to display at a specific frequency point. The detector was needed because the level of the signal under test could vary during the finite time period during which it was being measured by the analyzer. Common detector types include Average, +Peak, −Peak, Sample, and Quasi-Peak.
A problem with current detectors is that the user must choose the right detector for the particular signal and measurement combination the user is working with at the time. For example, when measuring power of a narrow-band signal, the +Peak detector is usually most appropriate, but the Average detector is usually most appropriate when measuring the level of the noise floor. Thus, detection methods are optimized for accurately displaying either signal levels or for noise levels, but not for both.
Embodiments of the invention address these and other limitations of the prior art.